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Lesson 1 / 4 · Commercial Button Mushroom Operator

Room Loading

How a room is filled on Monday decides how its air behaves for the next sixty days.

  • By the end you can explain why bed area sets the duty on your machine.
  • By the end you can spot a fill pattern that starves part of the room.
  • By the end you can record loading so a later problem can be traced.

Controlled room: how the air moves

Cooled, humid air drops from the overhead duct onto the beds, returns through the room, and 20 to 30 percent fresh air is mixed in. About 15 cm per second over the beds, 4 to 6 air changes an hour. Source: ICAR-DMR manual.

Perforated supply ductAHUcooling coilhumidifierreturnfresh air 20-30%
Supply airReturn airBeds

Read numerical examples with their source, method and crop context. They are not universal operating instructions. Historical prices are not current quotations.

Carbon dioxide from the bed10g per m2 per hourfirst two flushes, when load is highestSource: ICAR-DMR manual, 2011
Heat from the bed10W per m2at 17 C and 88 per cent humiditySource: ICAR-DMR manual, 2011
Water leaving the bed31g per m2 per hourat 17 C and 85 per cent humiditySource: ICAR-DMR manual, 2011
Air speed over the bed15cm per secondraise only if air is humidifiedSource: ICAR-DMR manual, 2011
Air changes in the first two flushes6per hour4 per hour from the third flushSource: ICAR-DMR manual, 2011
MIDH costed growing room60 x 18 x 16feettwo PUF rooms with corridorSource: MIDH Telangana guidelines, 2025-26
Conceptual commercial mushroom farm cutaway with separate growing and handling areas.
AI-generated teaching illustration · not field evidence
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See the whole operation

Notice
Receiving, growing, packing and dispatch need coordinated space.
Understand
Capacity is a whole-farm outcome, not just the number of racks.
Try it
Define the incoming compost stage and the product buyers will accept.
See where this fits in the full workflow →

01Bed area is the load

Every load DMR publishes is per square metre of bed. In the first two flushes a bed makes about 10 g of carbon dioxide per square metre every hour, about 10 W of heat per square metre, and loses about 31 g of water per square metre every hour at 17 C and 85 per cent humidity.

So if you add a tier and increase bed area, you increase cooling, ventilation and humidification duty in the same proportion. The machine does not know you added shelves.

DMR's project model assumes six crops of 60 days per room per year.

02Fill evenly or grow two crops in one room

Uneven filling is a common cause of staggered flushes. Compost depth, compaction and casing thickness must be the same from the first tray to the last.

Casing thickness is worth agreeing in writing, because DMR's manual defines casing as a 3 to 4 cm layer in one paragraph and instructs a 4 to 5 cm application a few lines later. Pick one figure for your farm and hold it.

A bed that is deeper at one end runs warmer there, pins later and is picked later, so one room then needs two climate decisions at once.

03Leave the air its path

Air must reach the back of the room and return. DMR limits air speed over the bed to 15 cm per second and asks for about 6 air changes per hour from venting to the end of the second flush, dropping to 4 later, with fresh air filtered to 2 micrometres.

That only happens if ducts, returns and doors stay clear. Rows pushed against a return, sheets hanging over a duct, or crates stacked in the corridor all change the map of the room.

Walk the loaded room before the crop starts and find the places where you feel no air.

04Case study: the last two rows

A unit growing in a 60 by 18 foot room, the size MIDH costs in its production unit norm, added two rows against the back wall to use spare compost.

Those rows sat past the end of the duct run. They read 2 C warmer, pinned two days late, and after a normal watering the caps there stayed wet longest, which is the blotch condition.

The operator did not change the set point. He pulled the rows back, cleared the return, remeasured at bed height and wrote the new layout into the room file.

Record one room loading

  1. Measure and write the bed area you actually filled, tier by tier.
  2. Weigh the compost per tray and note the depth at both ends.
  3. Measure casing thickness in six places and set the farm standard.
  4. Walk the loaded room and mark every place with no air movement.
  5. Draw the layout in the room file before the crop starts.

Write in your farm diary: Bed area, compost weight per tray, depths, casing thickness, dead air spots.

Mistakes that cost a crop

  • Adding beds without asking whether the machine carries the extra load.
  • Filling the last rows past the duct run to use spare compost.
  • Leaving depth and casing thickness to each worker's judgement.

Check yourself

Three questions, instant answers

  1. You add one more tier of beds in the same room. What changes?

  2. Two extra rows past the end of the duct run will probably:

  3. DMR's manual gives casing thickness as:

An editorial self-check, not a certificate. Answers are not stored, not even on this device.

Words used in this lesson

Bed area
Total growing surface in square metres across all tiers.
Duty
The work a machine must do to hold a target.
Return
The opening through which room air goes back to the unit.
Room file
The written record of layout, fill and readings.
References & further reading
Button mushroom cultivation and climate knowledge

Operating values require stage, strain, sensor and production-system context.

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The guide behind this lessonOpen the reference guide